src/test/test-bpf.c

/* SPDX-License-Identifier: LGPL-2.1+ */

#include <linux/bpf_insn.h>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>

#include "bpf-firewall.h"
#include "bpf-program.h"
#include "load-fragment.h"
#include "manager.h"
#include "missing.h"
#include "rm-rf.h"
#include "service.h"
#include "test-helper.h"
#include "tests.h"
#include "unit.h"
#include "virt.h"

/* We use the same limit here that PID 1 bumps RLIMIT_MEMLOCK to if it can */
#define CAN_MEMLOCK_SIZE (64U*1024U*1024U)

static bool can_memlock(void) {
        void *p;
        bool b;

        /* Let's see if we can mlock() a larger blob of memory. BPF programs are charged against
         * RLIMIT_MEMLOCK, hence let's first make sure we can lock memory at all, and skip the test if we
         * cannot. Why not check RLIMIT_MEMLOCK explicitly? Because in container environments the
         * RLIMIT_MEMLOCK value we see might not match the RLIMIT_MEMLOCK value actually in effect. */

        p = mmap(NULL, CAN_MEMLOCK_SIZE, PROT_READ|PROT_WRITE, MAP_ANONYMOUS|MAP_SHARED, -1, 0);
        if (p == MAP_FAILED)
                return false;

        b = mlock(p, CAN_MEMLOCK_SIZE) >= 0;
        if (b)
                assert_se(munlock(p, CAN_MEMLOCK_SIZE) >= 0);

        assert_se(munmap(p, CAN_MEMLOCK_SIZE) >= 0);
        return b;
}

int main(int argc, char *argv[]) {
        struct bpf_insn exit_insn[] = {
                BPF_MOV64_IMM(BPF_REG_0, 0), /* drop */
                BPF_EXIT_INSN()
        };

        _cleanup_(rm_rf_physical_and_freep) char *runtime_dir = NULL;
        CGroupContext *cc = NULL;
        _cleanup_(bpf_program_unrefp) BPFProgram *p = NULL;
        _cleanup_(manager_freep) Manager *m = NULL;
        Unit *u;
        char log_buf[65535];
        struct rlimit rl;
        int r;
        union bpf_attr attr;
        bool test_custom_filter = false;
        const char *test_prog = "/sys/fs/bpf/test-dropper";

        test_setup_logging(LOG_DEBUG);

        if (detect_container() > 0)
                return log_tests_skipped("test-bpf fails inside LXC and Docker containers: https://github.com/systemd/systemd/issues/9666");

        assert_se(getrlimit(RLIMIT_MEMLOCK, &rl) >= 0);
        rl.rlim_cur = rl.rlim_max = MAX3(rl.rlim_cur, rl.rlim_max, CAN_MEMLOCK_SIZE);
        (void) setrlimit(RLIMIT_MEMLOCK, &rl);

        if (!can_memlock())
                return log_tests_skipped("Can't use mlock(), skipping.");

        r = enter_cgroup_subroot();
        if (r == -ENOMEDIUM)
                return log_tests_skipped("cgroupfs not available");

        assert_se(set_unit_path(get_testdata_dir()) >= 0);
        assert_se(runtime_dir = setup_fake_runtime_dir());

        r = bpf_program_new(BPF_PROG_TYPE_CGROUP_SKB, &p);
        assert(r == 0);

        r = bpf_program_add_instructions(p, exit_insn, ELEMENTSOF(exit_insn));
        assert(r == 0);

        if (getuid() != 0)
                return log_tests_skipped("not running as root");

        r = bpf_firewall_supported();
        if (r == BPF_FIREWALL_UNSUPPORTED)
                return log_tests_skipped("BPF firewalling not supported");
        assert_se(r > 0);

        if (r == BPF_FIREWALL_SUPPORTED_WITH_MULTI) {
                log_notice("BPF firewalling with BPF_F_ALLOW_MULTI supported. Yay!");
                test_custom_filter = true;
        } else
                log_notice("BPF firewalling (though without BPF_F_ALLOW_MULTI) supported. Good.");

        r = bpf_program_load_kernel(p, log_buf, ELEMENTSOF(log_buf));
        assert(r >= 0);

        if (test_custom_filter) {
                attr = (union bpf_attr) {
                        .pathname = PTR_TO_UINT64(test_prog),
                        .bpf_fd = p->kernel_fd,
                        .file_flags = 0,
                };

                (void) unlink(test_prog);

                r = bpf(BPF_OBJ_PIN, &attr, sizeof(attr));
                if (r < 0) {
                        log_warning_errno(errno, "BPF object pinning failed, will not run custom filter test: %m");
                        test_custom_filter = false;
                }
        }

        p = bpf_program_unref(p);

        /* The simple tests succeeded. Now let's try full unit-based use-case. */

        assert_se(manager_new(UNIT_FILE_USER, MANAGER_TEST_RUN_BASIC, &m) >= 0);
        assert_se(manager_startup(m, NULL, NULL) >= 0);

        assert_se(u = unit_new(m, sizeof(Service)));
        assert_se(unit_add_name(u, "foo.service") == 0);
        assert_se(cc = unit_get_cgroup_context(u));
        u->perpetual = true;

        cc->ip_accounting = true;

        assert_se(config_parse_ip_address_access(u->id, "filename", 1, "Service", 1, "IPAddressAllow", 0, "10.0.1.0/24", &cc->ip_address_allow, NULL) == 0);
        assert_se(config_parse_ip_address_access(u->id, "filename", 1, "Service", 1, "IPAddressAllow", 0, "127.0.0.2", &cc->ip_address_allow, NULL) == 0);
        assert_se(config_parse_ip_address_access(u->id, "filename", 1, "Service", 1, "IPAddressDeny", 0, "127.0.0.3", &cc->ip_address_deny, NULL) == 0);
        assert_se(config_parse_ip_address_access(u->id, "filename", 1, "Service", 1, "IPAddressDeny", 0, "10.0.3.2/24", &cc->ip_address_deny, NULL) == 0);
        assert_se(config_parse_ip_address_access(u->id, "filename", 1, "Service", 1, "IPAddressDeny", 0, "127.0.0.1/25", &cc->ip_address_deny, NULL) == 0);
        assert_se(config_parse_ip_address_access(u->id, "filename", 1, "Service", 1, "IPAddressDeny", 0, "127.0.0.4", &cc->ip_address_deny, NULL) == 0);

        assert(cc->ip_address_allow);
        assert(cc->ip_address_allow->items_next);
        assert(!cc->ip_address_allow->items_next->items_next);

        /* The deny list is defined redundantly, let's ensure it got properly reduced */
        assert(cc->ip_address_deny);
        assert(cc->ip_address_deny->items_next);
        assert(!cc->ip_address_deny->items_next->items_next);

        assert_se(config_parse_exec(u->id, "filename", 1, "Service", 1, "ExecStart", SERVICE_EXEC_START, "/bin/ping -c 1 127.0.0.2 -W 5", SERVICE(u)->exec_command, u) == 0);
        assert_se(config_parse_exec(u->id, "filename", 1, "Service", 1, "ExecStart", SERVICE_EXEC_START, "/bin/ping -c 1 127.0.0.3 -W 5", SERVICE(u)->exec_command, u) == 0);

        assert_se(SERVICE(u)->exec_command[SERVICE_EXEC_START]);
        assert_se(SERVICE(u)->exec_command[SERVICE_EXEC_START]->command_next);
        assert_se(!SERVICE(u)->exec_command[SERVICE_EXEC_START]->command_next->command_next);

        SERVICE(u)->type = SERVICE_ONESHOT;
        u->load_state = UNIT_LOADED;

        unit_dump(u, stdout, NULL);

        r = bpf_firewall_compile(u);
        if (IN_SET(r, -ENOTTY, -ENOSYS, -EPERM))
                return log_tests_skipped("Kernel doesn't support the necessary bpf bits (masked out via seccomp?)");
        assert_se(r >= 0);

        assert(u->ip_bpf_ingress);
        assert(u->ip_bpf_egress);

        r = bpf_program_load_kernel(u->ip_bpf_ingress, log_buf, ELEMENTSOF(log_buf));

        log_notice("log:");
        log_notice("-------");
        log_notice("%s", log_buf);
        log_notice("-------");

        assert(r >= 0);

        r = bpf_program_load_kernel(u->ip_bpf_egress, log_buf, ELEMENTSOF(log_buf));

        log_notice("log:");
        log_notice("-------");
        log_notice("%s", log_buf);
        log_notice("-------");

        assert(r >= 0);

        assert_se(unit_start(u) >= 0);

        while (!IN_SET(SERVICE(u)->state, SERVICE_DEAD, SERVICE_FAILED))
                assert_se(sd_event_run(m->event, UINT64_MAX) >= 0);

        assert_se(SERVICE(u)->exec_command[SERVICE_EXEC_START]->exec_status.code == CLD_EXITED &&
                  SERVICE(u)->exec_command[SERVICE_EXEC_START]->exec_status.status == EXIT_SUCCESS);

        assert_se(SERVICE(u)->exec_command[SERVICE_EXEC_START]->command_next->exec_status.code != CLD_EXITED ||
                  SERVICE(u)->exec_command[SERVICE_EXEC_START]->command_next->exec_status.status != EXIT_SUCCESS);

        if (test_custom_filter) {
                assert_se(u = unit_new(m, sizeof(Service)));
                assert_se(unit_add_name(u, "custom-filter.service") == 0);
                assert_se(cc = unit_get_cgroup_context(u));
                u->perpetual = true;

                cc->ip_accounting = true;

                assert_se(config_parse_ip_filter_bpf_progs(u->id, "filename", 1, "Service", 1, "IPIngressFilterPath", 0, test_prog, &cc->ip_filters_ingress, u) == 0);
                assert_se(config_parse_exec(u->id, "filename", 1, "Service", 1, "ExecStart", SERVICE_EXEC_START, "-/bin/ping -c 1 127.0.0.1 -W 5", SERVICE(u)->exec_command, u) == 0);

                SERVICE(u)->type = SERVICE_ONESHOT;
                u->load_state = UNIT_LOADED;

                assert_se(unit_start(u) >= 0);

                while (!IN_SET(SERVICE(u)->state, SERVICE_DEAD, SERVICE_FAILED))
                        assert_se(sd_event_run(m->event, UINT64_MAX) >= 0);

                assert_se(SERVICE(u)->exec_command[SERVICE_EXEC_START]->exec_status.code != CLD_EXITED ||
                          SERVICE(u)->exec_command[SERVICE_EXEC_START]->exec_status.status != EXIT_SUCCESS);

                (void) unlink(test_prog);
                assert_se(SERVICE(u)->state == SERVICE_DEAD);
        }

        return 0;
}